/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Lucene.Net.Index
{
    /// <summary>
    /// Class to write byte streams into slices of shared
    /// byte[].  This is used by DocumentsWriter to hold the
    /// posting list for many terms in RAM.
    /// </summary>
    public sealed class ByteSliceWriter
    {
        private byte[] slice;
        private int upto;
        private readonly ByteBlockPool pool;

        int offset0;

        public ByteSliceWriter(ByteBlockPool pool)
        {
            this.pool = pool;
        }

        /// <summary>
        /// Set up the writer to write at address.
        /// </summary>
        /// <param name="address"></param>
        public void Init(int address)
        {
            slice = pool.buffers[address >> DocumentsWriter.BYTE_BLOCK_SHIFT];
            System.Diagnostics.Debug.Assert(slice != null);
            upto = address & DocumentsWriter.BYTE_BLOCK_MASK;
            offset0 = address;
            System.Diagnostics.Debug.Assert(upto < slice.Length);
        }

        /// <summary> 
        /// Write byte into byte slice stream
        /// </summary>
        public void WriteByte(byte b)
        {
            System.Diagnostics.Debug.Assert(slice != null);
            if (slice[upto] != 0)
            {
                upto = pool.AllocSlice(slice, upto);
                slice = pool.buffer;
                offset0 = pool.byteOffset;
                System.Diagnostics.Debug.Assert(slice != null);
            }
            slice[upto++] = b;
            System.Diagnostics.Debug.Assert(upto != slice.Length);
        }

        public void WriteBytes(byte[] b, int offset, int len)
        {
            int offsetEnd = offset + len;
            while (offset < offsetEnd)
            {
                if (slice[upto] != 0)
                {
                    // End marker
                    upto = pool.AllocSlice(slice, upto);
                    slice = pool.buffer;
                    offset0 = pool.byteOffset;
                }

                slice[upto++] = b[offset++];
                System.Diagnostics.Debug.Assert(upto != slice.Length);
            }
        }

        public int GetAddress()
        {
            return upto + (offset0 & DocumentsWriter.BYTE_BLOCK_NOT_MASK);
        }

        public void WriteVInt(int i)
        {
            while ((i & ~0x7F) != 0)
            {
                WriteByte((byte)((i & 0x7f) | 0x80));
                i = (int)((uint)i >> 7);
            }
            WriteByte((byte)i);
        }
    }
}
